1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording that is used for writing data on a recording medium by means of a perpendicular magnetic recording system, and more specifically, to a magnetic head for perpendicular magnetic recording that has a main pole and a shield.
2. Description of Related Art
The recording systems of magnetic read/write apparatuses include a longitudinal magnetic recording system wherein signals are magnetized in a direction along the plane of a recording medium (the longitudinal direction) and a perpendicular magnetic recording system wherein signals are magnetized in a direction perpendicular to the plane of a recording medium. It is known that the perpendicular magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of providing higher linear recording density, compared with the longitudinal magnetic recording system.
Magnetic heads for perpendicular magnetic recording typically have, like those for longitudinal magnetic recording, a structure where a read head section having a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head section having an induction-type electromagnetic transducer for writing are stacked on the top surface of a substrate. The write head section includes a main pole that produces a write magnetic field in the direction perpendicular to the plane of a recording medium. The main pole includes, for example, a track width defining portion having an end located in a medium facing surface that faces a recording medium, and a wide portion that is connected to the other end of the track width defining portion and is greater in width than the track width defining portion. The track width defining portion has a generally constant width. To achieve higher recording density, it is required that the write head section of the perpendicular magnetic recording system be smaller in track width and improved in write characteristics such as overwrite property which is a parameter indicating an overwriting capability.
A magnetic head for use in a magnetic disk drive such as a hard disk drive is typically provided in a slider. The slider has the medium facing surface mentioned above. The medium facing surface has an air inflow end (a leading end) and an air outflow end (a trailing end). The slider is designed to slightly fly over the surface of a recording medium by means of an airflow that comes from the air inflow end into the space between the medium facing surface and the recording medium.
Here, the side of positions closer to the leading end relative to a reference position will be defined as the leading side, and the side of positions closer to the trailing end relative to the reference position will be defined as the trailing side. The leading side is the rear side in the direction of travel of the recording medium relative to the slider. The trailing side is the front side in the direction of travel of the recording medium relative to the slider.
The magnetic head is typically disposed near the trailing end of the medium facing surface of the slider. In a magnetic disk drive, positioning of the magnetic head is performed by a rotary actuator, for example. In this case, the magnetic head moves over the recording medium along a circular orbit about the center of rotation of the rotary actuator. In such a magnetic disk drive, a tilt of the magnetic head with respect to the tangent of the circular track, which is called a skew, occurs according to the position of the magnetic head across the tracks.
In particular, in a magnetic disk drive of the perpendicular magnetic recording system which is higher in capability of writing on a recording medium than the longitudinal magnetic recording system, the skew mentioned above can cause the phenomenon that signals already written on one or more tracks that are adjacent to a track targeted for writing are erased or attenuated during writing of a signal on the track targeted for writing (such a phenomenon will hereinafter be referred to as adjacent track erasure). For achieving higher recording density, it is necessary to prevent adjacent track erasure.
A known technique for preventing adjacent track erasure induced by a skew is to configure the main pole so that its end face located in the medium facing surface decreases in width with increasing proximity to the top surface of the substrate, as disclosed in U.S. Patent Application Publication Nos. US 2004/0150910 A1 and US 2009/0059426 A1, for example. U.S. Patent Application Publication Nos. US 2004/0150910 A1 and US 2009/0059426 A1 also disclose configuring the main pole so that its thickness in the vicinity of the medium facing surface decreases with increasing proximity to the medium facing surface.
In order to prevent the problems induced by a skew, it is also effective to reduce the thickness of the main pole in the medium facing surface. If the entire main pole is thinned, however, the main pole becomes small in cross-sectional area perpendicular to the direction in which magnetic flux flows. This makes it difficult for the main pole to direct much magnetic flux to the medium facing surface, thus leading to degradation of overwrite property.
Configuring the main pole so that its thickness in the vicinity of the medium facing surface decreases with increasing proximity to the medium facing surface as disclosed in U.S. Patent Application Publication Nos. US 2004/0150910 A1 and US 2009/0059426 A1 allows the main pole to be small in thickness in the medium facing surface and allows part of the main pole away from the medium facing surface to be large in thickness, thereby making it possible for the main pole to direct much magnetic flux to the medium facing surface.
In order to prevent adjacent track erasure induced by a skew and provide higher recording density, it is effective to provide a write shield having an end face that is located in the medium facing surface at a position on the front side in the direction of travel of the recording medium relative to the end face of the main pole, as disclosed in U.S. Patent Application Publication No. US 2009/0059426 A1.
In view of the foregoing, in order to prevent adjacent track erasure induced by a skew and provide higher recording density, the magnetic head can conceivably be configured so that at least one of part of the top surface of the main pole in the vicinity of the medium facing surface and part of the bottom end of the main pole in the vicinity of the medium facing surface is formed into an inclined portion that is inclined relative to a direction perpendicular to the medium facing surface, and the write shield is provided with an inclined surface opposed to this inclined portion.
The above-described configuration, however, has a problem in that where the inclined portion of the main pole and the inclined surface of the write shield are opposed to each other over a large area with a small spacing therebetween, magnetic flux leakage from the main pole to the write shield increases to cause degradation of write characteristics such as the overwrite property.
To avoid this, the inclined surface may be reduced in length in the direction perpendicular to the medium facing surface. This, however, would result in a reduction in volume of the write shield and thereby compromise the function of the write shield. More specifically, a reduction in volume of the write shield is likely to cause magnetic flux saturation in the write shield. This in turn causes magnetic flux leakage from the write shield toward the medium facing surface, and thus raises a problem that the magnetic flux leakage may result in accidental erasure of data stored on the recording medium.
It has thus been difficult for a conventional magnetic head including a write shield to prevent the skew-induced problems and provide improved write characteristics without compromising the function of the write shield.